The present invention relates to a positioning unit with an accelerating nanodrive, which has a resolution of at least ±10 nm, a slider and a module which has a stationary component and a component movable for this purpose, which has a mass of less than 500 g and is movably supported relative to the drive. The invention also relates to a positioning apparatus with at least two such positioning units.
Such positioning units are used, for example, to move the object observed under a microscope. Here it is important that the drive makes for a preset position with an especially high resolution. This is achieved by the drive exerting acceleration on a slider and thereby moving the slider relative to the drive.
As a rule, high resolution is achieved by repeatedly moving the slider merely a particularly short distance. This distance lies in the nanometer range and the slider can be positioned with extremely high resolution by means of a plurality of such small movement steps.
In these nanodrives a distinction is made between clamping and accelerating methods. In clamping methods the slider is gripped, moved a short distance and then released again. The clamps quickly return to the initial position and grip the slider again to achieve another forward push again in the nanometer range.
The other group of nanodrives uses relatively high accelerations, which are generally higher than 10 G, as the drive principle. These can be inertial drives or drives which accelerate their movable component, that is the slider, by means of mechanical pulse waves. This group of nanodrives generally has a simpler structure and can therefore be designed as a smaller structural unit. Particularly compact forms of such nanodrives are described in DE 38 44 821 C2, EP 0 611 485 B1 and DE 44 40 758 A. This type of nanodrive will subsequently be called an accelerating nanodrive.
There is great interest in using said compact accelerating nanodrives for positioning the movable components of a module which has a mass of less than 500 g and is supported relative to the drive. However, it has been found that the accelerating nanodrive is not suitable for this purpose.
If such modules are brought in contact with an accelerating nanodrive, even if the components are correctly designed, no technically usable force transmission between the accelerating nanodrive and the movable component of the module is achieved. Even if the accelerating nanodrive can exert many times the force which would be required to accelerate the movable component of the module, the accelerating nanodrive is braked as soon as it comes in contact with the movable component of the guide module. Precision engineers using nanodrives had first tested the interaction of drive and module in a loose structure, as is usually the case when using these actuating drives, before they securely connected the units one to the other. In these tests the accelerating drives were generally inferior to the clamping drives and thus only clamping drives were used for generic positioning units. This led the practical workers to recognize that accelerating drives with nanometer precision are not suitable for positioning modules having a mass of less than 500 g.
All attempts to use such an accelerating nanodrive for positioning such a light movable component of the module have failed in that enlarging the drive initially met with no success and from a certain size of drive, preference was given to drives using clamping movement.
It would therefore be desirable and advantageous to provide an improved positioning unit which obviates prior art shortcomings and allows use of accelerating nanodrives.